One of the greatest challenges in muscle research is to find out the sequence of events leading to contraction. In amphibians, like frogs, there exist two different kinds of muscle fibers, slow and twitch. When either kind of fiber is stimulated, some electrical signals were detected that were thought to be due to the movement of some charges in the internal membrane linked to the surface membrane. These charge movements, presumably, trigger the release of calcium ions from an intracellular reservoir and, in turn, activate contraction. Experiments will be performed to compare the time course of charge movement and the time course of rise in tension in both fiber types. The anticipated results will give clues concerning the similarities and differences of contractile activation in both of them. Some agents, such as D2O and dantrolene sodium known to block contraction partially, will be applied to both fiber types to study their effect on charge movement and generation of tension. The information so obtained will be valuable for a deeper understanding of the properties of charge movement in relation to activating contraction as well as the action of these agents on striated muscle. It is hoped that these experiments will pave the path towards our long-term goal, i.e. to understand the proper functioning of cardiac and skeletal muscles which is required in the search for a cure for the cardiovascular and muscular diseases.